1. Field
The present invention relates to an optical technique that offers, for example, forgery prevention effect, decorative effect and/or aesthetic effect.
2. Related Art
Articles such as securities, certificates, brand goods, media for personal authentication, etc. are required to be difficult to forge. Thus, in some cases, a display excellent in forgery prevention performance is provided on such articles.
Most of the displays include a microstructure such as diffraction grating, hologram, lens array, etc. The microstructures are hard to analyze. Further, in order to manufacture a display including the microstructure, an expensive manufacturing apparatus such as electron beam writer or the like is necessary. For these reasons, the displays like this can achieve an excellent performance in forgery prevention.
For example, the patent literature 1 describes a display that includes first and second interface parts. The first interface part is provided with grooves as a relief-type diffraction grating. The second interface part is provided with recesses or protrusions which are disposed two-dimensionally with a center-to-center distance smaller than the minimum center-to-center distance of the grooves and each of which has a forward tapered shape. The display has a fine structure and special optical characteristics. Accordingly, the display has an excellent performance in forgery prevention.